Rotary switches are widely used in various mechanical apparatuses, such as a gas stove or a microwave oven, to exercise segmented control over the mechanical apparatuses as needed.
For example, a rotary switch for use with a gas stove is configured for use in adjusting the flow rate of a fuel gas. Referring to FIG. 1, the gas stove comprises a burner 11, a fuel gas flow rate controller 12, and an ignition device 13. The fuel gas flow rate controller 12 is disposed at a fuel gas inlet IN of the burner 11 and connected to a fuel gas source through a tube. A control level 14 is disposed at the front end of the fuel gas flow rate controller 12. A rotary switch 15 is disposed at one end of the control level 14. The ignition device 13 is positioned proximate to the mouth of the burner 11 and connected to a high-voltage coil disposed at the fuel gas flow rate controller 12. A rotation head 16 of the rotary switch 15 is rotated clockwise or counterclockwise to change the state of the rotary switch 15, so as to adjust the fuel gas flow rate and control the magnitude of the heat emitted from the gas stove.
In another example, a rotary switch for use with a microwave oven is configured for use in adjusting the magnitude of the heat of the microwave oven. Referring to FIG. 2, the rotary switch 20 comprises a body 21, a connection portion 22, a control unit 23, and a rotation head 24. The body 21 has therein a variable resistor. The body 21 is embeddedly disposed in microwave oven. The two ends of the connection portion 22 are connected to the body 21 and the control unit 23, respectively, to enable the body 21 to move together with the control unit 23. The rotation head 24 is disposed at the control unit 23 and positioned proximate to a user. The resistance produced by the body 21 varies as a result of the user's rotating the rotation head 24 to change the direction indicated by the rotation head 24; hence, the output current is adjusted according to the variable resistance. The operating state of the rotary switch 20 is determined according to the level of the current input to the body 21 by a related device disposed in the microwave oven, so as to adjust the magnitude of the heat generated.
However, regarding the aforesaid gas stove, if the pilot light of the ignition device 13 gets extinguished abnormally and the fuel gas flow rate controller 12 is not turned off immediately, a leak of the fuel gas may happen, thereby leading to an accident. Furthermore, in the above example of a microwave oven, the aforesaid resistive control inevitably generates an error and thus precludes precise control of the magnitude of the input current to the microwave oven. Moreover, after long use, the control unit 23 and the rotation head 24 are likely to end up in reduced precision or a failure.